Effects of intermediate- and long-term use of opioids on cognition in patients with chronic pain.

The authors review research on the intermediate- and long-term effects of taking opioid medication on cognitive functioning in patients with chronic cancer and noncancer pain. Opioids seem to be more likely to worsen cognitive performance during the first few days of use and during the first few hours after a given dose, particularly on timed performance in psychomotor tasks. Results have been inconsistent regarding what decrements in cognitive performance are observed when patients with chronic pain who have been using opioids for more than three days are compared with healthy volunteers. Relatively few differences have been found when cognitive performance in these patients is compared with their performance before taking opioids, or with the performance of a comparable pain population not taking opioids. Major unresolved questions remain regarding such important issues as effects of different types of opioids, dose effects, interactions with other medications, and subject variables.